The term is a mixture of Greek ("biblio" -- meaning books) and Latin ("bibulous" from "bibere" -- meaning to drink), and can be loosely translated as being drunk on books.
"bibliobibuli" was a term coined in 1957 by H. L. Mencken who said:
"There are people who read too much: the bibliobibuli. I know some who are constantly drunk on books, as other men are drunk on whiskey or religion. They wander through this most diverting and stimulating of worlds in a haze, seeing nothing and hearing nothing."